A disc brake caliper for a rail vehicle normally comprises a brake actuator, pivotable levers for transmitting a brake force from the actuator to the levers, brake pad holders, pivotally arranged at the lever ends, and means for connecting the different members of the caliper. The brake pad holders are provided with exchangeable brake pads of a friction material for braking cooperation with a brake disc, over which the disc brake caliper is mounted astraddle.
The brake actuator is normally a pneumatic brake unit, comprising a brake cylinder or brake actuator and a slack adjuster or brake regulator. The space for such a disc brake caliper in the vicinity of the brake disc in the undercarriage or bogie of the rail vehicle is very limited, and it is thus desired to keep the overall dimensions of the disc brake caliper at a minimum.
An example of a measure to minimize the dimensions is to decrease the length of the pivotable levers, which means that their angular movements during operation are increased. This in turn may lead to undesirably great movements of the suspended brake pad holders in relation to the brake disc.
For obtaining controlled braking, it is in principle desired to have a geometrically constant engagement of the brake pads with the brake disc irrespective of the wear of the brake pads and the disc and also of the axial position of the axially slightly movable brake disc in relation to the disc brake caliper.
In order to fulfill these requirements, a basic measure is to suspend the brake pad holders in such a way that they are only movable in a plane perpendicular to a center-line of the caliper. The journaling of the brake pad holders is in principle as stiff as possible in other directions. As the brake pad holders are suspended in the described fashion, relative movements of other members of the caliper must be allowed. A disc brake caliper shown in EP-A-1 357 009 has separately suspended brake pad holders, and the remainder of the caliper is suspended via a bush containing rubber sleeves for elastically allowing certain relative movements. The design of the bush is, however, such that relative movements in the plane of the caliper center-line are not possible due to metallic contact in the bush.
A disc brake caliper shown in U.S. Pat. No. 4,053,034 can be regarded as the closest prior art. Here, a rubber bushing for elastic suspension of brake levers in a disc brake caliper is shown. Two conical rubber sleeves fill compartments between a cylinder and a shaft. Hereby the stiffness is constant in all directions. These disc brake caliper designs do accordingly not fulfill the requirements set out above.